Over
the past decade, much information has been disseminated about
“critical periods” – windows of
plasticity, usually early in life, during which certain experiences
must happen in order for certain abilities to develop. This concept has
often been misapplied to suggest that only experiences early in life
count, and that development and plasticity shut down after a certain
point. This Network study has shown, however, that enriched experiences
later in life can “re-open” windows of plasticity
previously thought to be closed. Earlier experiments have shown that
young owls can effectively re-map their visual and auditory maps
(including literally re-mapping the brain representations of these
“maps”) when their visual input is manipulated by
putting prisms over their eyes. These owls quickly learn the new
relationships between auditory and visual input, and most adapt fully
to the new relationship. Adult owls, however, were largely unable to
adapt to the shifted input. This study demonstrated that adding an
“enriched” experience to these adult
owls’ lives – in this case, hunting live mice
instead of being fed dead mice – can radically increase the
plasticity of these adult owls’ visual and auditory systems,
allowing their brains to “re-map” and adapt
effectively to the new input. This new research challenges popular
notions of plasticity and critical periods. While the brain is
certainly very malleable early in life, it may never be too late for
remarkable brain changes to take place, given greater
“motivation” and appropriate stimulation. One
interesting finding in this enrichment experiment has been that the
degree of plasticity is correlated with the owls’ social
dominance. Further studies will investigate how social dominance might
contribute to plasticity, perhaps through greater access to resources
or as a function of different levels of stress; or conversely, how
greater plasticity may facilitate dominance status.